The candidates engaged in three debates: October 15, October 18 and October 25. The third debate took place Thursday, October 25 at 7 p.m. in Cincinnati. NBC White House Correspondent Chuck Todd moderated the debate with anchor/political reporter Colleen Marshall from WCMH in Columbus, anchor Sheree Paolello from WLWT in Cincinnati, and political reporter Tom Beres from WKYC in Cleveland. It was live on all Ohio NBC affiliates.[27]

Mandel, 34, was elected State Treasurer in 2010. Before that, he was a Lyndhurst City Councilman and Ohio State Representative. He was criticized as Ohio Treasurer for not fulfilling his pledge to serve a four-year term and for not attending any of the Board of Deposit monthly meetings.[31] However, Mandel raised a lot of money. He was called a rising star in the Republican Party and was called "the rock star of the party." He was also compared to Marco Rubio.[32]

Mandel's campaign was singled out by the independent fact-checking group Politifact for its "casual relationship with the truth" and its tendency to "double down" after inaccuracies were pointed out. The fact-checking group wrote: "For all the gifts Mandel has, from his compelling personal narrative as an Iraq war veteran to a well-oiled fundraising machine, whoppers are fast becoming a calling card of his candidacy."[33]

Mandel raised $7.2 million through the first quarter of 2012. He had $5.3 million cash on hand, trailing Brown's $6.3 million.[34] However, Mandel benefited from massive support from conservative out-of-state superPACs, which raise unlimited amounts of money from anonymous donors. These outside groups, including Crossroads GPS, aired over $60 million in TV advertising supporting Mandel and attacking Brown,[35] outspending Democratically-aligned outside groups by more than five-to-one.[36] Mandel's campaign was aided by over $1 million spent primarily on attack ads by a 501(c)(4) organization called the Government Integrity Fund. The group was funded by anonymous donors and run by lobbyist Tom Norris of Columbus, Ohio-based Cap Square Solutions.[37]